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Feeding Microbes: Nutrition, Microbiome, Metabolism, and Health (Oral Session 6)

(OR06-05-25) Uptake of Labeled Vitamin D by a Human Gut Commensal Bacteroides thetaiotaomicron

Sunday, June 1, 2025
10:48 AM – 11:00 AM ET
Location: S230 CD

    Presenting Author(s)

  • GW

    Grace Wilson, B.S.

    PhD Candidate
    Baylor University
    Waco, Texas, United States

    Disclosure(s): No relevant financial relationship(s) with ineligible companies to disclose.

    • Co-Author(s)

  • YC

    YongSun Cho

    Baylor University, United States

  • JW

    John L. Wood

    Baylor University, United States

  • Leigh Greathouse, PhD, MPH, MS, RD

    Associate Professor of Nutrition Sciences
    Baylor University
    Waco, Texas, United States

Objectives: Although the correlation between vitamin D (VD) deficiency and colorectal cancer (CRC) has been well established, the mechanism by which VD deficiency increases CRC risk and mortality remains unknown. VD is a known modulator of the gut microbiota composition, which is itself associated with CRC development. In our previous randomized placebo-controlled trial, VD supplementation increased microbial stability and abundance of Bifidobacterium and decreased abundance of Prevotella and Firmicutes compared to a placebo group. Given that VD functions as a microbiota modulator and its deficiency promotes a microenvironment favorable to CRC development, we propose that the gut microbiota directly imports VD. Certain gut bacteria, namely Bacteroides, are known to take up cholesterol and modify it through sulfur transferases. Given the structural similarity between cholesterol and VD, we hypothesize that gut microbiota also takes up VD through similar mechanisms.

Methods: We synthesized a VD-alkyne, which allows tracking of bacterial interaction and metabolism. Specifically, the VD-alkyne can be selectively stained with an azide dye to visualize uptake using click-chemistry. We incubated Bacteroides thetaiotaomicron (B. theta), a bacterium known to harbor sulfur transferase, with VD-alkyne or native VD for 48 hours. Confocal microscopy was used to visually identify the uptake of VD-alkyne vs native VD control.

Results: As visualized in fluorescent micrographs, B. theta readily takes up VD-alkyne from its environment. Negative controls using unlabeled native VD were not fluorescent.

Conclusions: B. theta B. theta takes up VD, we plan to analyze the metabolites within bacterial lyses after treatment with VD. The GC-MS analysis will reveal metabolites produced from VD uptake. This data can be used to uncover the mechanism by which bacteria import and metabolize VD. Determination of direct bacterial interaction with VD may provide novel mechanisms in understanding how VD contributes to microbiome function and its impacts on CRC development.

Funding Sources: None